End-mill tool with high and low helical flutes and related method for rough cutting and finishing a workpiece

ABSTRACT

An end-mill tool has at least one low helix angle flute, or primary flute) and at least two low helix angle flutes, or secondary flutes. The primary and secondary flutes intersect to define a plurality of compound helical cutting surfaces. Each of the compound cutting surfaces includes a cutting edge having a leading portion formed adjacent one of the primary flutes and a trailing portion formed adjacent one of the secondary flutes.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of U.S. Ser. No. 08/238,864filed May 6, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

In general, the present invention relates to machining of a workpiece.More particularly, the present invention relates to end-mill tools formilling a workpiece and a related method.

2. Background of the Invention

Rotary cutting end-mill tools are used for various machining operationson workpieces. Such machine operations are generically referred to asmilling operations and include the forming of slots, keyways, pockets,and the like. Several considerations related to end-mill tool designinclude time for completing a machining operation, amount of materialremoved in a cut, quality of the cut, and wear on the tool itself duringthe milling operation.

The various machining operations performed with an end-mill tool can beperformed in a "roughing" mode (rough cutting) and a "finishing" mode(finishing cutting). During roughing, material is removed from aworkpiece at a relatively high rate (e.g., depth of cut), but with arelatively rough surface finish. Finishing involves the removal ofmaterial from a workpiece at a relatively low rate, but with arelatively smooth surface finish. Generally, these two operations(roughing and finishing) are antithetical to one another, and requiretwo operations with two different end-mills.

End-mill tools are formed from materials such as tungsten carbide, highspeed steel, ceramic, and other advanced materials and coatings andtypically include a "shank" portion, a "body" portion and a "point". Theshank portion is located towards one end of the end-mill tool and isgenerally cylindrical (but may be tapered) for engagement by a spindleof a milling machine. In use, the milling machine rotatably drives theend-mill tool about its longitudinal axis. The body portion of theend-mill tool is located between the shank and the point. The point isformed at an opposite end of the tool from the shank portion, andtypically includes one or more cutting edges.

To manufacture an end-mill tool, a grinder is typically used to grind aflute face and a corresponding cutting edge on the body of the end-milltool. The grind (grinding operation) typically starts from a positionadjacent an end of the body portion and continues to a point at or nearthe interface of the body portion and the shank portion, commonlyreferred to as an "inception location". The grind forms a desiredhelical flute face and/or helical cutting edge. Prior art end-millstypically have continuous helical flutes with continuous cutting edgeshelically extending from the inception location to the point (orvice-versa). The flutes function primarily for chip removal, in a mannersimilar to the helical flutes found on an ordinary drill bit.

An end-mill tool representative of the end-mill tools of the prior artis illustrated in FIGS. 1A and 1B and identified with reference numeral100. The tool 100 has been formed of cylindrical rod stock which hasbeen ground to form distinctive portions. At one end of the tool 100 isa shank portion 102, suitable for chucking to the spindle of a millingmachine (not shown) for rotating and advancing the tool 100. At an otherend of the tool 100 is a point 104 which is provided with flat cuttingedges 114 and 116. Between the shank portion 102 and the point 104 is abody portion 106 which is helically ground to have a number of flutes110 and 112. A "boundary" between the body portion 106 and the shankportion 102 is designated 108 in the drawing.

In the embodiment illustrated, the formation of flutes in the bodyportion 106 generally involves the grinding of two channels, or flutes110 and 112, which form two diametrically-opposed positions at the point104 towards the shank portion 102. The grinding is discontinued at theboundary 108 of the body portion 106 and the shank portion 102. It willbe appreciated that the direction of the grind could, of course, bereversed. In a known variation referred to as a three-flute end-mill,three flutes wind helically around the body portion of the tool andterminating in three cutting edges. The flutes 110 and 112 are formed ata helix angle which "winds" around the cylindrical body portion.

Generally, the location of the flat cutting edges 114 and 116 isdetermined by the location of the flutes 110 and 112 at the point 104 ofthe tool 100. The end-mill tool 100 illustrated in FIG. 1A has twocutting edges 114 and 116 at the point 104. The number and location ofthe cutting edges 114 and 116 is determined by the flutes 110 and 112.FIG. 1B shows the cutting edges 114 and 116 of the tool 100 in greaterdetail.

It is known in the art to form flutes at a low helix angle or a highhelix angle. A "low helix" (or low helical flute) is a flute thathelically "winds" around a cylinder at an angle of no more than 45°(forty-five degrees). A "super" low-helical flute would be a flute thatwinds around a cylinder at an angle of at no more than 15°. A "highhelix" (or high helical flute) is a flute that helically winds around acylinder at an angle of greater than 45°. A "super" high-helical flutewould be a flute that winds around a cylinder at an angle of at least65°. Low helix angle flutes are typically employed for rough cuttingwhile high helix angle flutes are employed for finish cutting.

Returning to FIG. 1A, the tool 100 is illustrated to include two cuttingedges 120 and 122. Each of the cutting edges 120 and 122 is helical andfollows one of the flutes 110 and 112 helically around the body portion106. A notable feature of these cutting edges 120 and 122 is that theyare "continuous"--in other words they helically extend continuously fromthe point 104 to the shank 102. These cutting edges 120 and 122 functionto remove material in the linear direction of travel of the end-mill 100(e.g., from right-to-left, as viewed in FIG. 1A) during a machiningoperation when the end-mill is "buried" into a workpiece. Materialremoved from the workpiece will tend to be in the form of an elongatedhelical (curlicue) chip, and will be guided away from the workpiece bythe channels formed by the flutes 110 and 112.

By way of further definition, the edges 114 and 116 at the point 104 ofthe tool 100 can be considered to be "flat" cutting edges, and thecutting edges 120 and 122 along the body 106 of the tool 100 can beconsidered to be "helical" cutting edges.

The following U.S. Patents are further instructive of the prior art:U.S. Pat. Nos. 4,610,581; 5,049,009; 4,721,421; and 4,963,059. Thesepatents are incorporated by reference as if fully set forth herein.

Numerous variations of the grind (e.g., flute angle) have been attemptedfor end-mill tool design. Prior advancements relating to materialremoval and feed rate of end-mill cutters have been accomplished by (1)varying the spiral lead angle; (2) increasing the depth of the flutes inthe body portion of the end-mill, (3) changing the radial rake; (4)changing the clearance angles of the cutting edges; and (5) forming chipsplitting grooves in the flutes.

While such variations have proven successful in various applications,they are also associated with disadvantages and limitations. Forexample, such variations may weaken the core diameter of the end-millcutter, thereby weakening the tool. Additionally, such noted variationsare not suitable for a particular applications (e.g., regarding millingtime, rough cut, finish cut, etc.). Furthermore, known end-mills are notefficient for both rough cutting and finish cutting.

It is often advantageous when performing an end-mill machining operationto create many small chips, rather than fewer elongated curlicue chips.This allows, for example, rapid rate of removal of material from aworkpiece without undue heating of the end-mill tool. Heat is generallyanathema to tools, particularly end-mill tools. To the end of reducingheat, it is known to use coolants. Dry machining (sans coolant) offersan advantage of simplicity. Generally, the end-mill of the presentinvention provides for increased rate of removal without sacrificingtool life and strength, and may not require flowing coolant onto theworkpiece or tool.

SUMMARY OF THE INVENTION

It is therefore a principal object of the present invention to providean improved end-mill tool which overcomes the disadvantages andlimitations of known constructions, including but not limited to thosediscussed above.

It is a related object of the present invention to provide an end-milltool suitable for both roughing and finishing a workpiece.

It is another object of the present invention to provide an end-milltool which provides for a higher rate of chip removal.

It is a more specific object of the present invention to provide anend-mill tool which includes a low helix flute and a high helix flutewhich intersect to define a plurality of compound helical cuttingsurfaces.

Generally according to the present invention, these above noted andother objects are achieved by having two distinct sets of flutes, alow-helix angle set of primary flutes and a high-helix angle set ofsecondary flutes intersecting the primary flutes. At points ofintersection, compound helical cutting surfaces are defined whichfacilitate chip removal from a workpiece, thereby allowing for a highrate of chip removal.

In one preferred form, the present invention provides an end-mill toolwhich includes a shank, a point, and a main body portion locatedintermediate the shank and the point. A primary flute is formed on themain body portion along a first helix. A secondary flute is formed onthe main body portion along a second helix. The primary and secondaryflutes intersect one another. A compound helical cutting surface isdefined by the primary flute and the secondary flute. The compoundhelical cutting surface includes a continuous cutting edge having aleading portion formed adjacent a portion of the primary flute and atrailing portion formed adjacent a portion of the secondary flute.

In a more preferred form, the present invention provides a combinedroughing and finishing end-mill tool for forming a workpiece by removingchips from the workpiece. The end-mill tool includes a shank forengaging the end-mill tool to a rotating device and a point for plungingthe tool into the workpiece. The end-mill tool further includes a mainbody portion located intermediate the shank and the point. A primaryflute is formed on the main body portion along a first helix angle. Atleast two secondary flutes are formed on the main body portion along asecond helix angle. The at least two secondary flutes intersect theprimary flute. The primary flute and two secondary flutes cooperate todefine a plurality of compound helical cutting surfaces. Each of thecompound helical cutting surfaces includes a continuous cutting edgewhich is operative to remove chips from the workpiece of varying lengthssuch that chips having a first length are removed from the workpiecethrough the primary flute and chips having a second length are removedfrom the workpiece through the secondary flutes.

In another form, the present invention relates to a method for roughcutting and finishing a workpiece. The method comprises the step ofproviding an end-mill tool having a longitudinal axis, a primary flutedisposed at a low helix angle, and a secondary flute disposed at a highhelix angle. The primary and secondary flutes define a compound helicalcutting surface having a continuous edge. The continuous cutting edgehas a leading portion adjacent the primary flute with a first axiallength and a trailing portion adjacent said secondary flute with asecond axial length.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present invention willbecome apparent from analysis of the following written specification andaccompanying drawings and the appended claims in which:

FIG. 1A is a side view of an end-mill tool, representative of the priorart.

FIG. 1B is an end view of the end-mill tool of FIG. 1A.

FIG. 2 is a side view of an end-mill constructed in accordance with afirst preferred embodiment of the present invention, detailing thehelical flute face of the end-mill.

FIG. 3 is a side view of the end-mill of the first preferred embodimentof the present invention, from a different perspective than the view ofFIG. 2, detailing the helical cutting edge of the end-mill.

FIG. 4 is an end view of the end-mill of FIG. 2.

FIG. 5A is a partial plan view taken in the direction 5--5 of FIG. 2.

FIG. 5B is a cross-sectional view taken along the time 5B--5B of FIG.5A.

FIG. 6 is an enlarged side view of a portion of the end-mill of FIG. 2.

FIG. 7 is an enlarged simplified view of four vertically adjacent landsof the end-mill of the first preferred embodiment.

FIGS. 8 and 9 are simplified end views, illustrating alternateconstructions of the first preferred embodiment of the end-mill of thepresent invention.

FIG. 10 is a side view of an end-mill constructed in accordance with asecond preferred embodiment of the present invention, detailing thehelical flute face of the end-mill.

FIG. 11 is a side view of the end-mill of the second preferredembodiment of the present invention, from a different perspective thanthe view of FIG. 10, detailing the helical cutting edge of the end-mill.

FIG. 12 is an enlarged simplified view similar to FIG. 7, illustratingfour vertically adjacent lands of the second preferred embodiment andshowing the right stagger of the lands.

FIG. 13 is another enlarged simplified view similar to FIG. 7,illustrating an alternative arrangement to the second preferredembodiment having a left stagger of adjacent lands.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings in which preferred embodimentsare shown. It will be appreciated, however, that the present inventionmay be embodied in many other forms and should not be construed aslimited to the embodiments set forth herein. For purposes of clarity,the same reference numerals are used throughout the drawings toconsistently identify identical or equivalent element. In the discussionthat follows, it will be understood that no priority of function ismeant to be attributed to the terms "primary" and "secondary". In thisregard, these terms are used for identification purposes only.

First Preferred Embodiment of the Present Invention

Referring generally to FIGS. 2 through 7 of the drawings, an end-milltool constructed in accordance with the first preferred embodiment isidentified with reference numeral 200. FIGS. 2 and 3 illustrate two sideviews of the end-mill 200 of the present invention, taken ninety(circumferential) degrees from one another. FIG. 4 is an end view of theend-mill of FIGS. 2 and 3. FIGS. 5, 6 and 7 further show details of theend-mill 200. As will become evident, this embodiment is termed a "2×4"embodiment, since it has two primary flutes and four secondary flutes.

The end-mill tool 200 is shown to generally include a shank portion 202,a point 204 and a body portion 206. The end-mill has two primary flutes210 and 212 extending from the point towards the shank portion 202. Onlyone of the flutes 210 is visible in the view of FIG. 2.

The primary flutes 210 and 212 are formed at a relatively shallow helixangle β. In the embodiment illustrated, the helix angle β is preferablyapproximately 15°, which, according to the definitions set forth aboveis a super low-helix angle. At the point 204 of the tool 200, the twoprimary flutes 210 and 212 terminate and define a pair of flat cuttingedges 214 and 216, commonly referred to as end teeth cutting edges.

Further, in the embodiment illustrated, the end-mill has four secondaryflutes 220, 222, 224 and 226 which helically wind around the bodyportion 206 at a helix angle Θ which is different than the helix angleβ. It will be appreciated by those skilled in the art that the specificnumber of secondary flutes 220-226 is largely a matter of design choiceand subject to variation. The four secondary flutes 220-226 originatefrom four evenly-spaced virtual points (not shown) around thecircumference of the point 204, and terminate at four evenly-spacedvirtual points (not specifically shown) around the circumference of thebody portion 206 (e.g., at the intersection of the body portion and theshank portion 202). Preferably, the secondary flutes 220-226 are allformed along the same helix angle Θ. However, the secondary flutes220-226 can alternatively be formed at different angles relative to oneanother.

The two primary flutes 210 and 212 and the four secondary flutes 220-226intersect and cooperatively define a plurality of compound helicalcutting surfaces or lands 228. A side view of one of the lands 228 isshown in FIG. 6. The simplified side view of FIG. 7 illustrates therelative orientation of four axially adjacent lands 228. For purposes ofillustration, each of the lands 228 is shown to be equal in size andshape. As shown particularly in FIG. 2, depending on its location, aparticular land 228 (e.g. the uppermost land 228) may only be partiallyformed. The lands 228 illustrated in FIG. 7 are generally disposedradially between the first and second primary flutes 210 and 212. Itwill be understood that a corresponding number of lands 228, which aresubstantially identical in shape and form, are formed on acircumferentially opposing side of the tool 200.

The secondary flutes 220-226 are formed in the body portion 206 of thetool 200 at a relatively high helix angle Θ. Preferably the helix angleΘ of the secondary flutes 220-226 is approximately 65°, which, accordingto the definitions set forth above is a super high-helix angle. Thesecondary flutes 220-226 preferably intersect the primary flutes 210 and212 at an angle of at least 45°. In the exemplary embodimentillustrated, the primary flutes 210 and 212 intersect the secondaryflutes 220-226 at an angle of approximately 50° (i.e. the differencebetween the high helix angle Θ (65°) and the low helix angle β (15°)).

With specific reference to FIG. 6, each of the compound helical cuttingsurfaces 228 is formed to include a continuous cutting edge 230. Thesecutting edges 230 each includes a leading portion 232 and a trailingportion 234. The leading portions 232 are disposed at the intersectionof the secondary flutes 220-226 and the primary flute 210, and aredisposed at the low-helix angle β (e.g., 15°) which is determined by thehelix angle β of the primary flutes 210. Inasmuch as the angle of theleading portions 232 of the cutting edges 230 is determined by theprimary flute 210, they are considered to be "low-helical" cuttingedges. As shown in the simplified view of FIG. 7, the leading portions232 of the cutting edges 230 are aligned along a straight line 233.

Each trailing portion 234 of the cutting edges 230 originates from thetop of a respective leading portion 232 and helically winds around aportion of the body portion 206. These trailing portions 234 are locatedat the interface of the compound surface 228 and a respective secondaryflute 220-226, and are disposed at the high-helix angle Θ (e.g., 65°)which is determined by the helix angle Θ of the secondary flutes220-226. Inasmuch as the angle of the trailing portions 234 isdetermined by the secondary flutes 220-226, they are considered to be"high-helical" cutting edges.

With continued reference to FIG. 6, adjacent pairs of leading portions232 and trailing portions 234 are provided with a common cutting relief236 and a common clearance relief 238 behind the cutting relief 236. Thecutting relief 236 includes a leading portion 236a adjacent the leadingportion 232 and a trailing portion 236b adjacent the trailing portion234 of the cutting edge 234. Similarly, the clearance relief 238includes a leading portion 238a adjacent the leading portion of thecutting relief 236 and a trailing portion 238b adjacent the trailingportion 236b of the cutting relief 236. The cutting relief 236 allowsfor radial clearance during milling operation.

An important feature of the present invention is that the leadingportion 236a of the cutting relief 236 "runs into" (intersects, and iscontinuous with) the trailing portion 236b of the cutting relief 236.Likewise, the leading portion 238a and trailing portions 238b of theclearance relief 238 run into one another.

In the embodiment illustrated, the trailing portions 234 of the cuttingedges 230 have an axial dimension (as measured along the longitudinalaxis of the tool 200), from a one edge to the next, of a dimension L₂.The axial (vis-a-vis the longitudinal axis of the tool 200) extent ofeach of the leading portions 232 is each of a dimension L₁. Thesedimensions L₁ and L₂ are of particular interest and are discussed ingreater detail hereinbelow.

As mentioned above, the helix angle β of the primary flutes 210 and 212is preferably low, on the order of 15°, and the helix angle Θ of thesecondary flutes is preferably high, on the order of 65°. An importantfeature of the invention is that the leading portion 232 and associated(e.g., on the same flute surface) trailing portion 234 form a contiguouscutting edge 230 of dimension L₁ +L₂ for improved chip removal.

Provided that the rotational speed of the tool 200 is sufficient, thechips removed from the workpiece by the leading and trailing portions232 and 234 of the cutting edges 230 will correspond in length to theirrespective axial lengths L₁ or L₂. More particularly, a single chip isformed by the continuous cutting edge 230. Splitting of the chip willoccur at an intersection 240, or corner, of the leading portion 232 andthe trailing portion 234. Chips cut from the trailing portion 234 will"flow" through the respective adjacent secondary flute (e.g., 220-226).Chips cut from the leading portion 232 will flow through the associatedlow helical flute (e.g., 210 or 212).

In certain applications, the leading and trailing portions 232 and 234will remove one chip (without chip splitting) having a lengthcorresponding to the sum of their axial dimensions (L₁ +L₂). Forexample, if the rotational speed of the tool 200 is not sufficient, thesplitting of the chips at the intersection 240 may not occur. Therequired rotational speed depends primarily upon the material of theworkpiece and the amount of material being removed from the workpiece.Therefore, it may be desirable to incorporate additional chip splitting(breaking) structures (not shown, such as grooves) on the trailingportions 234 for machining under such circumstances. Such structuresinclude grooves (not shown) and the like, and are well known in the art.

The present invention contemplates a range of helix angles for theprimary flutes 210 and 212 and for the secondary flutes 220-226 inaddition to the low and high helix angles β and Θ set forth hereinabove.Evidently, it is important that the primary and secondary sets of flutesintersect one another. The present invention further contemplates:

primary flute helix angles β of at least 0°, but preferably no more than45°, although primary flutes having helix angles greater than 45° arepossible; and

secondary flute helix angles Θ of no more than 65°, although secondaryflutes having helix angles greater than 65° is possible.

It is also within the scope of the present invention that the primaryflutes 210 and 212 are angled in a different direction relative to thesecondary flutes 220-226 in which case, for example, the two helixangles β and Θ could be equal in magnitude but different in direction.For example, a set of primary flutes 210 and 212 may have a left-handhelix angle of 30°, and a set of secondary flutes 220-226 may have aright-hand helix angle of 30°. These angles, although equal inmagnitude, are different (in direction) than one another, which willcause the primary flutes 210 and 212 and the secondary flutes 220-226 tointersect one another on the body portion 206 of the tool 200.

The helix angles can be modified over a wide range. For example,specific applications may include, but by no means are limited to, thefollowing:

primary flutes 210 and 212 at 15°, secondary flutes 220-226 at 65°;

primary flutes 210 and 212 at 30°, secondary flutes 220-226 at 60°; and

primary flutes 210 and 212 at 50°, secondary flutes 220-226 at 80°.

The method of forming the tool 200 of the present invention generallyincludes the following steps:

1. providing a generally cylindrical tool blank (not shown);

2. grinding the primary flute 210 at the low helix angle β into the bodyportion 206;

3. grinding the second primary flute 212 at the low helix angle β intothe body portion 206;

4. grinding the first secondary flute 220 at the high helix angle Θ intothe body portion 206;

5. grinding the second secondary flute 222 at the high helix angle Θinto the body portion 206;

6. grinding the third secondary flute 224 at the high helix angle Θ intothe body portion 206;

7. grinding the fourth secondary flute 226 at the high helix angle Θinto the body portion 206;

8. grinding continuous cutting reliefs 236 on each of the compoundhelical cutting surfaces 228 by following the low helix angle β untilthe intersection point 240 and following the high helix angle Θthereafter;

9. grinding continuous clearance reliefs 238 on each of the compoundhelical cutting surfaces 228 by following the low helix angle β untilthe intersection point 240 and following the high helix angle Θthereafter;

10. grinding reliefs and clearances at the point 204 to form the cuttingedges 214-216.

Alternative constructions to the first preferred embodiment of theend-mill 200 of the present invention are provided in the simplified endviews of FIGS. 8 and 9. For example, FIG. 8 illustrates a simplified endview of an embodiment of an end-mill 300 having three primary flutes302, 304, and 306 which are visible in an end view looking onto thepoint of the end-mill 300. With three secondary flutes (not shown), thiswould be termed a "3×3" end-mill. FIG. 9 illustrates an embodiment of anend-mill 350, the invention having four primary flutes 352, 354, 356,and 358 which are visible in an end view looking onto the point of theend-mill. With four secondary flutes (not shown), this would be termed a"4×4" end-mill.

Various embodiments of an end-mill may be fabricated according to thetechniques set forth hereinabove by varying parameters such as helixangles β and Θ, spacing of a plurality of discrete low-helical leadingportions 232, and the like. Further alternative embodiments from thepreviously-described embodiments principally in the number of primaryand secondary flutes formed. Generally, since each one-or-more ("N")primary flute is typically intersected at least once by each one-or-more("M") secondary flute, various end-mills can be fabricated having "N×M"configurations. It will be readily appreciated that the presentinvention is not limited to any particular number of flutes or discretelow-helix angle cutting edges.

Second Preferred Embodiment of the Present Invention

With reference now to FIGS. 10 through 12, an end-mill tool 400constructed in accordance with a second preferred embodiment of thepresent invention is illustrated. The reference numerals used for thefirst preferred embodiment have been applied to drawings for the secondpreferred embodiment to identify identical or equivalent elements.

The first and second preferred embodiments differ only in that theleading portions 232 of the cutting edges 230 of the second preferredembodiment are staggered to the right progressing from the point 204 tothe shank 202 (e.g., a staggered right hand spiral). This isspecifically shown in FIG. 12 by the right stagger of the line 233. Byincorporating a stagger for certain applications, the leading portions232 of the cutting edges 230 engage the workpiece at different times,thereby reducing the cutting forces for milling a workpiece and alsoreducing the required energy, such as spindle horsepower. In someapplications, such an arrangement may further facilitate chip removal.

Turning now to FIG. 13, a simplified side view of the adjacent lands 228similar to FIG. 12 illustrating an alternative construction of thesecond preferred embodiment of the present invention is shown. In thisalternative construction, the cutting edges 232 are staggered to theleft progressing from the point 204 to the shaft 202 (e.g., a staggeredleft hand spiral).

The specific method of the present invention contemplates use of one ofthe above-described embodiments or alternatives thereto and includes thestep of rotating the end-mill tool (e.g., 200) about its longitudinallyaxis. The method further includes the steps of removing a firstplurality of chips from the workpiece through the primary flute andremoving a second plurality of chips from the workpiece through thesecondary flutes. In the preferred method, the chips of the firstplurality of chips each have a length which is substantially equivalentto the axial length L₁ of the leading portion 232 and the chips of thesecond plurality of chips each are substantially equivalent in length tothe axial length L₂ of the trailing portion 234 of the cutting edge 230.

The preferred embodiments and alternatives discussed above all assumethat the primary and secondary flutes each are formed along right handhelix. In certain applications, it may be desired to incorporate a lefthand helix. For example, such an orientation may be desired wheredownward transfer of removed chips is preferred.

The above, and other objects, features, advantages and embodiments ofthe invention, including other embodiments of the techniques discussedabove may become apparent to one having ordinary skill in the art towhich this invention most nearly pertains, and such other and additionalembodiments are deemed to be within the spirit and scope of the presentinvention. For example, the compound helical cutting surfaces which aredescribed as being integrally formed with the tool may alternatively beprovided on removable inserts. In certain applications, carbide insertsmay be braised to a steel body or alternatively mounted to the steelbody with suitable fasteners.

What is claimed is:
 1. An end-mill for performing a machining operationon a workpiece, the end-mill comprising:a shank; a point; a main bodyportion located intermediate said shank and said point; at least oneprimary flute formed on said main body portion along a first helixangle; said at least one primary flute defining a primary helicalcutting surface, at least one secondary flute formed on said main bodyportion along a second helix angle, said at least one secondary flutedefining a secondary helical cutting surface, said primary and secondaryflutes intersecting; and said corresponding primary and secondaryhelical cutting surfaces intersecting to form a compound helical cuttingsurface, said compound helical cutting surface including a continuouscutting edge having a leading cutting edge formed along a portion ofsaid primary helical cutting surface and a trailing cutting edge formedalong a portion of said secondary helical cutting surface.
 2. Theend-mill according to claim 1, wherein said at least one primary fluteand said at least one secondary flute define a plurality of compoundhelical cutting surfaces.
 3. The end-mill according to claim 2, saidleading portions of said continuous cutting edges of said plurality ofcompound helical cutting edges are staggered from a common line.
 4. Theend-mill according to claim 1, further comprising a cutting reliefincluding a leading portion formed adjacent said portion of said leadingcutting edge and a trailing portion formed adjacent said portion of saidtrailing cutting edge, said leading portion and said trailing portionintersecting.
 5. The end-mill according to claim 3, further comprising aclearance relief including a leading portion formed adjacent saidleading portion of said cutting relief and a trailing portion formedadjacent said trailing portion of said cutting relief.
 6. The end-millaccording to claim 1, wherein said second helix angle is greater thansaid first helix angle.
 7. The end-mill according to claim 1, whereinthe end-mill has at least two primary flutes and at least two secondaryflutes.
 8. The end-mill according to claim 1, wherein said secondaryflute is disposed on the main body portion at a high-helix angle, andsaid at least one primary flute is disposed on the main body portion ata low-helix angle.
 9. The end-mill according to claim 8, wherein saidhigh-helix angle is at least 45° greater than the low-helix angle.
 10. Acombined roughing and finishing end-mill tool for forming a workpiece byremoving chips from the workpiece, the end-mill tool comprising:a shankfor engaging the end-mill tool with a rotating device for rotating theend-mill tool about a longitudinal axis; a point for plunging the toolinto the workpiece; a main body portion located intermediate said shankand said point; at least one primary flute formed on said main bodyportion along a first helix; said at least one primary flute defining aprimary helical cutting surface; a least one secondary flute formed onsaid main body portion along a second helix angle, said at least onesecondary flute defining a secondary helical cutting surface, said atleast one secondary flute intersecting said at least one primary flute;said primary and secondary helical cutting surfaces intersecting; and aplurality of compound helical cutting surfaces defined by said primaryand secondary cutting surfaces, each of said compound helical cuttingsurfaces including a continuous cutting edge operative to remove chipsof varying lengths from the work piece such that chips having a firstlength are removed from the workpiece through the at least one primaryflute and chips having a second length are removed from the workpiecethrough the at least one secondary flute.
 11. The combined roughing andfinishing end-mill tool of claim 8, wherein said continuous cutting edgeincludes a leading portion formed adjacent said at least one primaryflute and a trailing portion formed adjacent one of said secondaryflutes.
 12. The combined roughing and finishing end-mill tool of claim9, wherein said leading portion of said continuous cutting edges has anaxial dimension substantially equivalent to said first length.
 13. Thecombined roughing and finishing end-mill tool of claim 10, wherein saidtrailing portion of said continuous cutting edges has an axial dimensionsubstantially equivalent to said second length.
 14. The combinedroughing and finishing end-mill tool of claim 10, wherein said firsthelix angle is a low helix angle and said second helix angle is a highhelix angle.
 15. A method of rough cutting and finishing cutting aworkpiece, the method comprising the steps of:providing an end-mill toolhaving a longitudinal axis, a primary flute disposed at a low helixangle and a secondary flute disposed at a high helix angle, said primaryand secondary flutes intersecting to form a compound helical cuttingsurface having a continuous cutting edge, said continuous cutting edgehaving a leading portion along said primary flute with a first axiallength and a trailing portion along said secondary flute with a secondaxial length; removing a first plurality of chips from the workpiecethrough said primary flute; and removing a second plurality of chipsfrom the workpiece through said secondary flute.